A variety of mechanisms have been proposed which allow an agent, such as a robot, to determine its location within an environment and to navigate within that environment. In an approach referred to as Simultaneous Localization and Mapping (SLAM), the agent builds a map of the environment in the course of navigation within that environment. In the SLAM approach, the agent may receive information from various sensors, including visual sensors. However, there remains room for considerable improvement in known localization and navigation mechanisms.